An Ottawa contracting firm has won a federal contract to help with the massive remediation of a contaminated southern Ontario industrial site.

Hamilton Harbour was identified as an “area of concern” under the Canada-United States Great Lakes Water Quality Agreement in 1985 because of poor water quality caused by years of intensive shoreline industrial and urban development.

Within the harbour is a 148-acre area known as Randle Reef. According to the federal government, there is 695,000 cubic metres – enough to fill three hockey arenas – of contaminated sediment at the bottom of the harbour.

Cleaning it up is expected to take eight years and cost $138.9 million, which will be split by the federal and provincial governments and well as various municipal bodies, the Hamilton Port Authority and industrial firm Stelco.

Work started in September 2015 with the construction of a 15-acre containment facility. Late last month, a joint venture consisting of Ottawa’s Milestone Environmental and British Columbia’s Fraser River Pile & Dredge received a $32.9-million contract for the second phase of the project that consists of dredging contaminated sediment and relocating the material to the containment facility via an underwater pipeline.

Milestone says it specializes in projects that involve soil and groundwater remediation, barrier walls and water treatment, among other service areas. The company previously participated in the cleanup of LeBreton Flats, while government contracting records show its B.C. office has remediated areas of the Whitehorse International Airport.

The federal government says it expects Milestone’s work to start in 2018 and take two years. Afterwards, the project will move to a third and final stage of removing water from the contaminated sediment, compacting it and placing a cap on the facility.

The cleanup of Randle Reef is expected to improve the health of the local fish population, create a cleaner water supply for humans and lead to waterfront development as Hamilton Harbour is removed from the list of Great Lakes Areas of Concern when the project is completed in 2022.